Converting the UK's transport fleet to electric vehicles will be pointless if they are recharged from a dirty grid, says Royal Academy report

Britain would have to almost entirely strip carbon emissions from its electricity grid to make a national switch to electric vehicles worthwhile, according to a report released this week.

In the report, Electric Vehicles: Charged with Potential, the Royal Academy of Engineering said that 20 million electric vehicles would generate as much carbon indirectly as fossil fuel-powered vehicles, unless energy production for the electricity grid that charges them is switched to renewable sources.

"It is difficult to see how electric vehicles fed from the present UK electricity generation mix are significantly better in terms of carbon emissions than petrol or diesel vehicles," said the report.

2020 targets for vehicle emissions stand at 130g of carbon dioxide per kilometre travelled, although some expect the target to drop over time, the report said. Current carbon emissions per kilometre travelled in an electric vehicle stand at about 100g, based on the relatively high proportion of fossil fuel-based generating plants in the UK.

Citing the UK Government's target of an 80 per cent reduction in emissions by 2050, the report said that electric vehicles would have to draw the bulk of their power from non-fossil sources.

"To have a major effect commensurate with the 2050 target, the introduction of EVs would need to be accompanied by almost total decarbonisation of the electricity supply," the report suggested.

The other big problem facing widespread EV takeup in the UK is peak demand. While the country's power generation capacity is high enough to support 20 million EVs in principle, the effect of vehicle charging on peak demand would probably mean that there is not enough energy available at the times when it is needed, such as when people are charging at work, and in the early evenings before they head home.